The present invention relates to disc recorders and, more specifically, to recorders in which video information is recorded on a rapidly rotating magnetic disc. The disc used in such a recorder may be constructed of either rigid or flexible material. The recording disc is rapidly rotated and one or more transducer heads are positioned adjacent the recording surface to record and reproduce the video information. In flexible disc recorders, the transducer head, when properly positioned, will actually contact the disc surface. The pressure applied to the disc surface by the transducer head, however, must be relatively slight so that the magnetic coating on the disc is not scraped or otherwise damaged.
Recording of video signals on the disc may be accomplished in a number of ways but the best format for many applications is one in which a number of concentric circular recording tracks are defined on the disc surface. The transducer is moved only intermittently between tracks during recording or playback. Generally one field of video information will be stored in each of the tracks and the magnetic disc will be rotated at a rate equivalent to the field rate of the video signal.
One type of transducer mounting arrangement designed to control transducer head to disc contact is shown in U.S. Pat. No. 3,814,441, issued June 4, 1974 to Craggs. A slotted finger on the side of the flexible disc opposite the transducer urges the disc against the transducer. While this arrangement may be acceptable where a single sided recording disc is being used, the finger would interfere with a second transducer if video recording were to be accomplished on both sides of the disc. Additionally, if the bottom surface of the disc were coated with magnetic material, the finger would cause significant wear of this material.
Another type of transducer mounting arrangement suitable for use with a flexible magnetic disc is U.S. Pat. No. 3,770,907, issued Nov. 6, 1973, to Hall and assigned to the assignee of the present invention. The Hall patent shows a transducer mounted for movement toward and away from a flexible magnetic disc. The transducer is urged into contact with the disc by a counterweighted lever system. The counterweight functions as an inertial mass to provide a constant force which the transducer head exerts against the recording disc. The transducer mounting arrangement shown in the Hall patent is somewhat limited by the face that the counterweight and lever mechanism must be moved as the transducer head is stepped radially to different recording tracks. The overall inertia of the transducer mounting is therefore a limitation on the speed of movement of the transducer.